[The context to this question is Hawking's radical prediction in 1974 that black holes could emit thermal radiation, thereby allowing some black holes to ultimately shrink and disappear. The cosmic microwave background radiation is the remnant radiation left over from the Big Bang.]
In the slow inflationary scenario, the cosmic microwave background radiation is not Hawking radiation. However, the fluctuations in the microwave background detected by WMAP [a NASA spacecraft] can be regarded as Hawking radiation from the inflationary period. Thus, in a sense, Hawking radiation has already been observed. So maybe I should get a Nobel Prize.
According to general relativity, white holes, the opposite of black holes [and] which spew matter into the universe, can exist. But we've never found them. What would we see with our telescopes if we did?
When black holes are large, things fall in. But they give off very little Hawking radiation. So they are essentially black. But when they are very small, they radiate more than they accrete. So they are essentially white. Black and white holes are the same, just with different boundary conditions. If the boundary conditions are that particles are going in but nothing is coming out, we call it a black hole. On the other hand, if the boundary conditions are that particles are going out but nothing is coming in, we call it a white hole.
If black holes are created in the Large Hadron Collider, will we be in danger of getting eaten up by them?
[This question refers to the construction outside Geneva, Switzerland, of the world's most powerful collider, which is expected to begin operations this summer. Some skeptics fear it will generate such powerful energies that it could create mini-black holes.]
The LHC is absolutely safe.
There is no danger that collisions between particles at the LHC will cause a rip in space-time and destroy the universe.
Particles from collisions far greater than those in the LHC occur all the time in cosmic rays, but nothing terrible happens.
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After his talk, Hawking was wheeled out of Beckman Auditorium to a standing ovation. He then took a victory lap in his wheelchair around the building, while the crowd snapped pictures and shouted: "We love you, Stephen."
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john.johnson@latimes.com
